MEK would be the solvent I'd use use for chemically welding ABS, Acrylic, PVC or Styrene. It's the active ingredient in commercial cements for all of these. For ABS cements, it typically makes up 3x-4x the percentage of Acetone, the rest is ABS material dissolved in that solution for viscosity variation.

The same is true for Acrylic Cement. In my Sign Shop, we dissolved acrylic in pure MEK or commercially available Acrylic cements in order to thicken the mixture when necessary.

Acetone is the most simple of the Ketones, MEK being far more volatile. It's an educated guess on my part that MEK is diluted with Acetone to give a longer "open time" or "working window" to allow the plastics (most commonly pipe and fittings for plumbing in terms of ABS.) being welded to be mooshed together just right before it sets up in the joint.

For acrylic and ABS case assembly or repair, the parts are aligned ahead of time and held in place for a hairline fit and pure, or almost pure, MEK is squirted with syringe or hypodermic type needle on an assembly bottle. The bottles are made of polyurethane, which cannot be dissolved or chemically welded in the manner of the other plastics I've mentioned. Capillary action sucks the MEK into the full surface of the hairline and welds almost instantaneously.

I can go into it in more depth, but it's really better to do your own research.

Be SURE to read the MSDS sheets on anything you decide to use.